1. Field of the Invention
The present invention relates to an image processing apparatus for executing an image correction to digital image data for recording.
2. Description of the Related Art
An image copying apparatus includes an input apparatus unit and an output apparatus unit. An image of an input original document is optically read out by a scanner as an input apparatus unit, a predetermined image process is executed to the read image, and thereafter, printing is executed according to a predetermined recording method by the output apparatus unit.
A concentration change of an edge (outline) portion of the image (multi-value data) obtained by optically reading the original by the scanner is more gentle than that of an edge portion of the original image. If such an image (multi-value data) is printed as it is onto a recording medium, an image whose sharpness has been deteriorated is obtained.
To solve such a problem, hitherto, there is such a technique that when a distribution shape of an image signal at a target point is upwardly convex, the image signal is converted into an image emphasis signal larger than the image signal at the target point, and when the distribution shape of the image signal is downwardly convex, the image signal is converted into the image emphasis signal smaller than the image signal at the target point. There is also such a technique that if the distribution shape of the image signal is neither upwardly convex nor downwardly convex, the image signal is converted into one of the original image signal and a signal replaced by an unsharp signal (for example, refer to the Official Gazette of Japanese Patent No. 2620368).
There is also such a technique that a value of the target pixel is replaced by a replacement pixel value formed by using the target pixel of the image and a pixel adjacent to the target pixel (for example, refer to Japanese Patent Application Laid-Open No. 07-288768).
Further, as for such an inconvenience that not only the sharpness is deteriorated but also a dot drop-out and an elimination of a thin line at the time of reduction occur, there is a method of avoiding the inconvenience by changing a resolution of one of the data input apparatus and the data output apparatus (for example, refer to Japanese Patent Application Laid-Open No. 2004-056252).
There is also such a technique that a zoom ratio and a width of outline of an image can be freely adjusted (for example, refer to Japanese Patent Application Laid-Open No. 10-200733). When the user magnifies or reduces the image, since the width of outline is changed, such a technique is effective to suppress that an inconvenience occurs in the image of the edge portion due to a zooming (variable magnification process).